CD9 and susceptibility to pneumonia measurement: - Augmented phagocytosis: EVs boost macrophage and monocyte bacterial phagocytosis. EVs containing enriched miRNAs enhanced the engulfment of bacteria (50) - Immunomodulation: EVs modulate leukotriene and immune signaling (e.g., transfer of miR-145 inhibited MRP1, elevating LTB4 levels, aiding in bacterial killing) (50). EV PD-L1 cargo engaged PD-1 on immune cells to dampen excessive inflammation in pneumonia (39)